Phosphor composition and light emitting device using the same

ABSTRACT

Disclosed herein are phosphor compositions which can exhibit a broad emission spectrum and improved color rendering index (CRI) relative to conventional phosphor materials. The phosphor compositions may, in some embodiments, be represented by the Formula I: (RE 2−x+y Ce x Ak 1−y )(MG 4−z−r Si r Mn z )(Si 1−e P e )O 12−r N r , wherein RE comprises at least one rare earth metal; Ak comprises at least one alkaline earth metal; MG comprises at least one main group element; x is greater than 0 and less than or equal to 0.2; y is less than 1; z is greater than 0 and less than or equal to 0.8; e is about 0 or less than or equal to 0.16; r is about 0 or less than or equal to 1; and z is about the sum of e and y. Also disclosed herein are lighting apparatuses including the phosphor compositions, as well as methods of making and using the phosphor compositions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. Application No.61/363,148, filed Jul. 9, 2010. The contents of this application arehereby incorporated by reference in their entirety.

BACKGROUND

1. Field

The present application relates to garnet oxide phosphor compositionsco-doped with Ce and Mn, as well as methods of making the same. Thepresent application also relates to lighting devices including saidcomposition.

2. Description

Solid state light emitting devices, such as light emitting diode (LED),organic light emitting diode (OLED) or sometimes called organicelectroluminescent device (OEL), and inorganic electroluminescent device(IEL), are widely utilized for various applications such as flat paneldisplays, indicators for various instruments, signboards, and ornamentalillumination, etc. Improving the efficiency of these light emittingdevices, especially LED, may provide higher luminescence intensitiescomparable to general purpose lighting devices, such as fluorescent andincandescent lamps. A white-LED, especially with a high color renderingindex (CRI) and low correlated color temperature (CCT), shows promise asa replacement for existing general purpose lighting devices.

Conventionally, white-LED includes the combination of blue-LED andyellow light emitting YAG phosphor powder dispersed in an encapsulatingresin, such as an epoxy or silicone (see e.g, U.S. Pat. Nos. 5,998,925and 6,069,440). However, this YAG:Ce type LED system exhibits low CRIdue to the lack of red luminescence. Accordingly, there is a need forphosphors providing broad spectral emission over a wider range ofwavelengths, as well as simple processes for preparing these phosphors.

One approach for obtaining a broad emission spectrum has been to use Ceas an activator to provide a wide emission spectrum with peak positionsfrom the green (about 480 nm to about 580 nm) to orange regions (about585 nm to about 620 nm). Because the emission of Ce ions is associatedwith electron transitions from 5d orbitals, the emission spectra can beshifted by other cations present in the host lattice. It is reportedthat Lu₂CaAl₄SiO₁₂:Ce exhibits green emission when excited by blue LED(U.S. Pat. No. 7,029,602). Thus, Lu₂CaAl₄SiO₁₂:Ce exhibits ablue-shifted emission relative to Y₃Al₅O₁₂:Ce, which results from thesmaller ionic size of Lu.

Mn ions usually exhibit emission in the green or red region dependingupon the crystalline structure and lattice position. As such, Mn ionscould theoretically improve the emission spectra of existing phosphors.Nevertheless, Mn ions poorly absorb blue light, and therefore onlyexhibit luminescence when excited by UV radiation. Consequently, Mn isnot typically used in conventional white-LEDs having blue-LEDs to excitethe luminescent phosphors.

SUMMARY

Some embodiments disclosed herein include a phosphor compositioncomprising a compound represented by the formula(RE_(2−x+y)Ce_(x)Ak_(1−y))(MG_(4−z−r)Si_(r)Mn_(z))(Si_(1−e)P_(e))O_(12−r)N_(r),wherein: RE comprises at least one rare earth metal; Ak comprises atleast one alkaline earth metal; MG comprises at least one main groupelement; x is greater than 0 and less than or equal to 0.2; y is lessthan 1; z is greater than 0 and less than or equal to 0.8; e is about 0or less than or equal to 0.16; r is about 0 or less than or equal to 1;and z is about the sum of e and y.

In some embodiments, MG is selected from the group consisting of Al, Sc,In, Ga, B, Si and combinations thereof. In some embodiments, MG is Al.

In some embodiments, RE is selected from the group consisting of Lu, Y,Gd, Tb, Sm, Pr and combinations thereof. In some embodiments, RE is Lu.

In some embodiments, Ak is selected from the group consisting of Mg, Ca,Ba, Sr and combinations thereof. In some embodiments, Ak is Ca.

In some embodiments, r is about 0. In some embodiments, e is about 0.

In some embodiments, the compound is represented by the formula(Lu_(2.16−x)Ce_(x))Ca_(0.84)Al_(3.84)Mn_(0.16)SiO₁₂, wherein x isgreater than 0.0025 and less than 0.2. In some embodiments, x is about0.16.

In some embodiments, the compound is represented by the formula(Lu_(1.84+z)Ce_(0.16))Ca_(1−z)(Al_(4−z)Mn_(z))SiO₁₂, wherein z isgreater than 0 and less than 0.8. In some embodiments, z is about 0.04.In some embodiments, z is about 0.02.

In some embodiments, e is greater than 0. In some embodiments, thecompound is represented by the formula(Lu_(1.84)Ce_(0.16))Ca(Al_(4−z)Mn_(z))(Si_(1−z)P_(z))O₁₂, wherein z isat least about 0.01 and less than about 0.16. In some embodiments, z isabout 0.02. In some embodiments, z is about 0.04.

In some embodiments, r is greater than 0.001. In some embodiments, e isabout 0. In some embodiments, x is about 0.16. In some embodiments, r isabout 0.4. In some embodiments, r is about 1. In some embodiments, z isabout 0.16.

In some embodiments, the composition is represented by the formulaselected from the group consisting of(Lu_(1.86)Ce_(0.16)Ca_(0.98))(Al_(3.98)Mn_(0.02))SiO₁₂,(Lu_(1.88)Ce_(0.16)Ca_(0.96))(Al_(3.96)Mn_(0.04))SiO₁₂,(Lu_(1.84)Ce_(0.16))Ca(Al_(3.98)Mn_(0.02))(Si_(0.98)P_(0.02))O₁₂ and(Lu_(1.84)Ce_(0.16))Ca(Al_(3.96)Mn_(0.04))(Si_(0.96)P_(0.04))O₁₂.

In some embodiments, the compound is represent by the formula(Lu_(2−x+z)Ce_(x)Ca_(1−z))(Al_(4−z−r)Si_(r)Mn_(z))SiO_(12−r)N_(r),wherein: x is greater than about 0.001 and less than about 0.4; z isgreater than about 0.001 and less than about 0.4; and r is greater thanabout 0.2 and less than or equal to about 1.

In some embodiments, the compound is represented by the formula selectedfrom the group consisting of(Lu_(2.0)Ce_(0.16)Ca_(0.84))(Al_(3.44)Si_(0.40)Mn_(0.16))SiO_(11.6)N_(0.40)and (Lu_(2.0)Ce_(0.16)Ca_(0.84))(Al_(2.84)Si_(1.0)Mn_(0.16))SiO₁₁N₁.

In some embodiments, the phosphor composition comprises a particulatethat includes the compound.

In some embodiments, the phosphor composition is a sintered ceramicplate.

In some embodiments, the compound emits radiation at a peak wavelengthbetween about 500 nm and about 650 nm when exposed to radiation having awavelength of about 450 nm.

In some embodiments, the compound has a first wavelength of peakemission between about 515 nm and about 560 nm and a second wavelengthof peak emission between about 600 and about 615 nm.

Some embodiments disclosed herein include a lighting apparatuscomprising: a light source configured to emit blue radiation; and thephosphor composition, wherein the phosphor composition is configured toreceive at a least a portion of the blue radiation. In some embodiments,the blue radiation has a wavelength of peak emission between about 430nm to about 550 nm. In some embodiments, the blue radiation has awavelength of peak emission of about 450 nm. In some embodiments, thelighting apparatus has a color rendering index (CRI) of at least 90.

Some embodiments disclosed herein include a method of producing lightcomprising exposing the phosphor composition to a blue radiation. Insome embodiments, the blue radiation has a wavelength of peak emissionbetween about 430 nm to about 550 nm. In some embodiments, the blueradiation has a wavelength of peak emission of about 450 nm. In someembodiments, the light has a color rendering index (CRI) of at least 90.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary lighting apparatus including a powder form ofa phosphor composition.

FIGS. 2A-B shows exemplary lighting apparatuses including emissivelayers having a phosphor composition.

FIG. 3 shows the excitation spectrum forLu_(2.0)Ce_(0.16)Ca_(0.84)Al_(3.84)Mn_(0.16)SiO₁₂.

FIG. 4 shows the emission spectrum forLu_(2.0)Ce_(0.16)Ca_(0.84)Al_(3.84)Mn_(0.16)SiO₁₂ when excited by blueradiation.

FIG. 5 shows the emission spectrum of different phosphor compositionshaving varying amounts of Ce when excited by blue radiation.

FIG. 6 shows the emission spectrum of different phosphor compositionshaving varying amounts of Mn when excited by blue radiation.

FIG. 7 shows the quantum efficiencies of different phosphor compositionshaving varying amounts of Ce when excited by blue radiation.

FIG. 8 shows the quantum efficiencies of different phosphor compositionshaving varying amounts of Mn when excited by blue radiation.

FIG. 9 shows the emission spectrum of different phosphor compositionshaving varying host lattices when excited by blue radiation.

FIG. 10 shows the emission spectrum of(Lu_(1.92)Ce_(0.08))Ca_(0.84)(Al_(0.96)Mn_(0.04))₄SiO₁₂ and YAG:Ce whenexcited by blue radiation.

FIG. 11 shows the emission spectrum of a sintered ceramic plate havingLu_(2.0)Ce_(0.16)Ca_(0.84)Al_(3.84)Mn_(0.16)SiO₁₂ when excited by blueradiation.

FIG. 12 shows the emission spectrum of a plasma synthesized powderhaving Lu_(2.0)Ce_(0.16)Ca_(0.84)Al_(3.84)Mn_(0.16)SiO₁₂ when excited byblue radiation.

DETAILED DESCRIPTION

Disclosed herein are phosphor compositions exhibiting a broad emissionspectrum and capable of being excited by blue light. Applicants havesurprisingly found the addition of Manganese (Mn) to Cerium (Ce)-dopedgarnet phosphors, particularly Lu₂CaAl₄SiO₁₂, provides a broad emissionspectrum when excited by blue radiation. In particular, the broademission spectrum can exhibit two wavelengths of peak emission which maybe attributable to Ce and Mn co-dopants. Without being bound to anyparticular theory, it is believed that Ce ions absorb blue radiation,and in turn, transfer energy to Mn ions which otherwise do notilluminate under blue radiation. Thus, the combination of Ce and Mndopants synergistically provide a broad emission spectrum when receivingblue radiation from a standard blue LED. In contrast, phosphors dopedonly with Mn ions only illuminate under UV radiation, and phosphorsdoped only with Ce ions exhibit a narrower emission spectrum.

The phosphor compositions of the present application can providesuperior lighting features over existing phosphors when implemented instandard LED lighting devices. As an example, the phosphor compositionsmay exhibit an improved CRI relative to existing phosphors. Accordingly,the phosphor compositions exhibit superior properties which may provideimproved lighting devices suitable for general lighting purposes.

Phosphor Compositions

The phosphor compositions, in some embodiments, may be represented bythe Formula I:(RE_(2−x+y)Ce_(x)Ak_(1−y))(MG_(4−z−r)Si_(r)Mn_(z))(Si_(1−e)P_(e))O_(12−r)N_(r),wherein RE comprises at least one rare earth metal; Ak comprises atleast one alkaline earth metal; MG comprises at least one main groupelement; x is greater than 0 and less than or equal to 0.2; y is lessthan 1; z is greater than 0 and less than or equal to 0.8; e is 0 orless than or equal to 0.16; r is 0 or less than or equal to 1; and z isabout the sum of e and y.

In some embodiments, MG is selected from Al, Sc, In, Ga, B, Si andcombinations thereof. In some embodiments MG is Al. In some embodiments,MG is Sc, In, Ga, B or Si. MG may also be a combination of at least twoelements (e.g., two, three, four, five, or six) selected from Al, Sc,In, Ga, B, and Si. As an example, MG may be a combination of a firstelement and a second element, each selected from Al, Sc, In, Ga, B, andSi. The molar ratio of the first element to the second element can be,for example, at least about 10 to 90; at least about 20 to 80; at leastabout 40 to 60; or at least about 1 to 1. The molar ratio of firstelement to the second element can also be, for example, no more thanabout 90 to 10; no more than about 80 to 20; no more than about 60 to40; or no more than about 1 to 1. In some embodiments, MG is acombination where the first element is Al. In some embodiments, MG is acombination where the second element is In. In some embodiments, MG is acombination where the second element is Ga. For example, MG may be acombination of Al and Ga with a molar ratio of about 1 to 1.

In some embodiments, RE is selected from Lu, Y, Gd, Tb, Sm, Pr andcombinations thereof. In some embodiments, RE is Lu. RE may also be acombination of at least two elements (e.g., two, three, four, five, orsix) selected from Lu, Y, Gd, Tb, Sm, and Pr. As an example, RE may be acombination of a first element and a second element, each selected fromLu, Y, Gd, Tb, Sm, and Pr. The molar ratio of the first element to thesecond element can be, for example, at least about 10 to 90; at leastabout 20 to 80; at least about 40 to 60; or at least about 1 to 1. Themolar ratio of the first element to the second element can also be, forexample, no more than about 90 to 10; no more than about 80 to 20; nomore than about 60 to 40; or no more than about 1 to 1. In someembodiments, RE is a combination where the first element is Lu. In someembodiments, RE is a combination where the second element is Y. Forexample, RE may be a combination of Lu and Y with a molar ratio of about1 to 1.

In some embodiments, Ak is selected from Mg, Ca, Ba, Sr and combinationsthereof. In some embodiments, Ak is Ca. In some embodiments, Ak is Mg.Ak may also be a combination of at least two elements (e.g., two orthree) selected from Ca, Ba, and Sr. As an example, Ak may be acombination of a first element and a second element each selected fromCa, Ba, and Sr. The molar ratio of the first element to the secondelement can be, for example, at least about 10 to 90; at least about 20to 80; at least about 40 to 60; or at least about 1 to 1. The molarratio of the first element to the second element can also be, forexample, no more than about 90 to 10; no more than about 80 to 20; nomore than about 60 to 40; or no more than about 1 to 1. In someembodiments, Ak is a combination where the first element is Ca. In someembodiments, Ak is a combination where the second element is Ba. Forexample, Ak may be a combination of Ca and Ba with a molar ratio ofabout 1 to 1.

In a preferred embodiment, MG is Al, RE is Lu and Ak is Ca. For example,some preferred phosphor compositions may be represented by Formula II:(Lu_(2−x+y)Ce_(x)Ca_(1−y))(Al_(4−z−r)Si_(r)Mn_(z))(Si_(1−e)P_(e))O_(12−r)N_(r),where x is greater than 0 and less than or equal to 0.2; y is less than1; z is greater than 0 and less than or equal to 0.8; e is 0 or lessthan or equal to 0.16; r is 0 or less than or equal to 1; and z is aboutthe sum of e and y.

The relative amounts of the components recited in Formulae I and II isnot particularly limited. A person of ordinary skill, guided by theteachings of the present application, may select appropriate amounts foreach component in the phosphor composition based upon the intendedlighting purpose. For example, as shown in Example 2, the relativeamounts of co-dopants can be modified to adjust the relative size of thepeaks in the emission spectrum, as well as the quantum efficiencies.Similarly, as another example, the composition of the host lattice willalso modify the relative peaks of the emission spectrum.

Thus, increasing the amount of Ce³⁺ obtains a red shift in the Ce³⁺emission wavelength. Meanwhile, increasing the amount of Mn²⁺ obtains ablue shift in the Ce³⁺ emission wavelength and a red shift in Mn²⁺emission wavelength. In the case of host modification, adding Gd or Tbincreases the Mn²⁺ emission.

Nevertheless, in some embodiments, the addition of Mn dopant into thephosphor composition of Formula I creates a charge imbalance which ispreferably neutralized by adjusting the amounts of RE, Ak, and Prelative to the amount of Ce and Mn.

The variable x can be, for example, at least about 0.001; at least about0.01; or at least about 0.02. The variable x can also be, for example,no more than about 0.18 or no more than about 0.16. Exemplary values forx include, but are not limited to, about 0.08 and about 0.16.

The variable y, in some embodiments, is equal to about the differencebetween z and e (e.g., y=z−e). The variable y can be, for example, atleast about 0.001; at least about 0.01; or at least about 0.02. Thevariable y can also be, for example, no more than about 0.8; no morethan about 0.4; and no more than about 0.2. Exemplary values of yinclude, but are not limited to, 0, about 0.02, about 0.04, and about0.16. In some embodiments, y is approximately the same as z.

The variable z can be, for example, at least about 0.001; at least about0.01; or at least about 0.02. The variable z can also be, for example,no more than about 0.5; or no more than about 0.4. Exemplary values forz include, but are not limited to, about 0.02, about 0.04, and about0.16. In some embodiments, z is about the sum of e and y. In someembodiments, z is approximately the same as e. In some embodiments, z isapproximately the same as y.

The variable e, in some embodiments, is equal to the difference betweenz and y (e.g., e=z−y). The variable e can be, for example, at leastabout 0.001; at least about 0.01; or at least about 0.02. The variable ecan also be, for example, no more than about 0.16; no more than about0.12; or no more than about 0.08. Exemplary values for e include, butare not limited to, 0, about 0.02 and about 0.04. In some embodiments, eis approximately the same as z.

The variable r can be, for example, at least about 0.001; at least about0.01; at least about 0.1; or at least about 0.2. The variable r can alsobe, for example, no more than about 1; or no more than about 0.6.Exemplary values of r include, but are not limited to, 0, about 0.4, andabout 1.

In some embodiments, r is 0. For example, the phosphor compositions maybe represented by Formula III:(RE_(2−x−y)Ce_(x)Ak_(1−y))(MG_(4−z)Mn_(z))(Si_(1−e)P_(e))O₁₂, where RE,Ak, MG, x, y, z and e can be the same defined in Formula I. Non-limitingexamples of phosphor compositions represented by Formula III include(Lu_(1.86)Ce_(0.16)Ca_(0.98))(Al_(3.98)Mn_(0.02))SiO₁₂,(Lu_(1.88)Ce_(0.16)Ca_(0.96))(Al_(3.96)Mn_(0.04))SiO₁₂,(Lu_(0.84)Ce_(0.16))Ca(Al_(3.98)Mn_(0.02))(Si_(0.98)P_(0.02))O₁₂ and(Lu_(1.84)Ce_(0.16))Ca(Al_(3.96)Mn_(0.04))(Si_(0.96)P_(0.04))O₁₂.

In some embodiments, e is 0. As an example, the phosphor compositionsmay be represented by Formula IV:(RE_(2−x+z)Ce_(x)Ak_(1−z))(MG_(4−z−r)Si_(r)Mn_(z))SiO_(12−r)N_(r), whereRE, Ak, MG, x, y, z and r can be the same as in any of the embodimentsof Formula I. Examples of phosphor compositions represented by FormulaIV include, but are not limited to,(Lu_(1.86)Ce_(0.16)Ca_(0.98))(Al_(3.98)Mn_(0.02))SiO₁₂,(Lu_(1.88)Ce_(0.16)Ca_(0.96))(Al_(3.96)Mn_(0.04))SiO₁₂,(Lu_(2.0)Ce_(0.16)Ca_(0.84))(Al_(3.44)Si_(0.40)Mn_(0.16))SiO₁₁₆N_(0.40)and (Lu_(2.0)Ce_(0.16)Ca_(0.84))(Al_(2.84)Si_(1.0)Mn_(0.16))SiO₁₁N₁.

In some embodiments, r is 0 and e is 0. The phosphor composition can,for example, be represented by Formula V:(RE_(2−x+z)Ce_(x)Ak_(1−z))(MG_(4−z)Mn_(z))SiO₁₂, where RE, Ak, MG, x andz are the same as defined in Formula I. In some embodiments, thephosphor composition is represented by Formula V, where z is about 0.16,and x is greater than about 0.025 and less than about 0.2, or preferablyx is about 0.16. In some embodiments, x is about 0.16, and z is greaterthan 0 and less than about 0.8. In some embodiments, z is about 0.02 orz is about 0.04. Some exemplary phosphor compositions represented byFormula V include, but are not limited to,(Lu_(1.86)Ce_(0.16)Ca_(0.98))(Al_(3.98)Mn_(0.02))SiO₁₂ and(Lu_(1.88)Ce_(0.16)Ca_(0.96))(Al_(3.96)Mn_(0.04))SiO₁₂.

In some embodiments, e is greater than 0, and r is 0. For example, thephosphor compositions may be represented the compound of Formula VI:(RE_(2−x+y)Ce_(x)Ak_(1−y))(MG_(4−z)Mn_(z))(Si_(1−e)P_(e))O₁₂, where RE,Ak, MG, x, y, z and e are the same as defined in Formula I. In someembodiments, the phosphor compositions are represented by Formula VI,and y is about 0. As an example, the phosphor compositions are representby Formula VII: (RE_(2−x)Ce_(x)Ak)(MG_(4−z)Mn_(z))(Si_(1−z)P_(z))O₁₂,where RE, Ak, MG, x and z are the same as defined in Formula I. In someembodiments, x may be about 0.08 or about 0.16. In some embodiments, zis greater than about 0.01 and less than about 0.16, about 0.02 or about0.04. Exemplary phosphor compositions represented by Formulas VI and VIIinclude, but are not limited to,(Lu_(1.92)Ce_(0.08))Ca(Al_(3.98)Mn_(0.02))(Si_(0.98)P_(0.02))O₁₂,(Lu_(1.92)Ce_(0.08))Ca(Al_(3.96)Mn_(0.04))(Si_(0.96)P_(0.04))O₁₂,(Lu_(1.84)Ce_(0.16))Ca(Al_(3.98)Mn_(0.02))(Si_(0.98)P_(0.02))O₁₂ and(Lu_(1.84)Ce_(0.16))Ca(Al_(3.96)Mn_(0.04))(Si_(0.96)P_(0.04))O₁₂.

In some embodiments, r is greater than about 0.001. In some embodiments,r is greater than about 0.001 and e is 0. For example, the phosphorcompositions may be represented by Formula VIII:(RE_(2−z−z)Ce_(x)Ak_(1−z))(MG_(4−z−r)Si_(r)Mn_(z))SiO₁₂. _(r)N_(r),where RE, Ak, MG, x, z and r can be the same as in any of theembodiments of Formula I. In some embodiments, the phosphor compositionsare represented by Formula VIII, where r is about 0.4. In someembodiments, the phosphor compositions are represented by Formula VIII,where r is about 1.0. In some embodiments, the phosphor compositions arerepresented by Formula VIII, where x is about 0.16. In some embodiments,the phosphor compositions are represented by Formula VIII, where z isgreater than about 0.001 and less than about 0.4 (preferably z is about0.16). Non-limiting examples of phosphor compositions represented byFormula VIII include(Lu_(2.0)Ce_(0.16)Ca_(0.84))(Al_(3.44)Si_(0.40)Mn_(0.16))SiO_(11.6)N_(0.40)and(Lu_(2.0)Ce_(0.16)Ca_(0.84))(Al_(2.84)Si_(1.0)Mn_(0.16))SiO_(11.6)N₁.

The phosphor compositions of the present application may advantageouslyexhibit a broad emission spectrum when excited by blue radiation. Thephosphor composition may, in some embodiments, emit radiation at a peakwavelength between about 500 nm and about 650 nm when exposed toradiation having a wavelength of about 450 nm. The phosphor compositionmay, in some embodiments, have a first wavelength of peak emissionbetween about 515 nm and about 560 nm and a second wavelength of peakemission between about 600 and about 615 nm. In some embodiments, thecomposition exhibits a third wavelength of peak emission between about730 nm and about 770 nm.

The phosphor composition may also exhibit a high color rendering index(CRI) and/or low correlated color temperature (CCT). The phosphorcomposition can exhibit a CRI of at least about 70 when exposed to blueradiation. The blue radiation may have a peak wavelength, for example,in the range of 350 nm to 550 nm, or about 450 nm. In some embodiments,the CRI is at least about 80; at least about 85; at least about 90; orabout 91. Meanwhile, the reference CCT may be in the range of 2500 K toabout 10000 K; in the range of about 2500 K to about 5000 K; in therange of about 2500 K to about 4500 K; or in the range of about 2600 toabout 3400 K.

In some embodiments, the phosphor composition can be in particulate form(e.g., a powder). The particulate may, for example, have an averageparticle size of less than about 1 mm; less than about 500 μm; less thanabout 100 μm; or less than about 1 μm. The particulate may also, forexample, have an average particle size of no more than about 1 nm; nomore than about 50 nm; no more than about 100 nm; no more than about 500nm; or no more than about 1 μm. In some embodiments, the particulate hasan average particle size in the range of about 1 nm to about 1 mm. Asdiscussed further below regarding the lighting apparatuses, the phosphorpowder may be encapsulated (or dispersed) within a resin, such as anepoxy.

The phosphor composition may include varying amounts of the one or morecompounds represented by any one of Formulae I-VIII. In someembodiments, the phosphor composition includes at least about 1% byweight of one or more compounds represented by any one of FormulaeI-VIII. In some embodiments, the phosphor composition includes at leastabout 10% by weight of one or more compounds represented by any one ofFormulae I-VIII. In some embodiments, the phosphor composition includesat least about 25% by weight of one or more compounds represented by anyone of Formulae I-VIII. In some embodiments, the phosphor compositionincludes at least about 50% by weight of one or more compoundsrepresented by any one of Formulae I-VIII. In some embodiments, thephosphor composition includes at least about 75% by weight of one ormore compounds represented by any one of Formulae I-VIII.

The total light transmittance of each of the phosphor composition atabout the peak wavelength of emission, or about the peak wavelength ofthe photoluminescent spectrum of the phosphor composition, may, in someembodiments, be at least about 25% of the theoretical total lighttransmittance; at least about 40% of the theoretical total lighttransmittance; or at least about 60% of the theoretical total lighttransmittance.

Methods of Making Phosphor Compositions

The phosphor compositions of the present application, such as thoserepresented by any one of Formulae I-VIII, may be prepared usingconventional techniques known by a person skilled in the art. As anexample, the phosphor compositions may be produced using known solidstate reaction processes for the production of phosphors by combining,for example, elemental oxides, carbonates and/or hydroxides as startingmaterials. Other starting materials may include nitrates, sulfates,acetates, citrates, or oxalates. Alternately, coprecipitates of the rareearth oxides can be used as the starting materials for the RE elements.Si may be provided via SiO₂, silicic acid, or other sources such asfumed silica.

In one example process of making the above phosphors, an array slurrymethod can be used. Raw materials (e.g., Lu₂O₃, Y₂O₃, Gd₂O₃, Tb₄O₇,Sm₂O₃, Pr₆O₁₁, CaCO₃, BaCO₃, SrCO₃, MnCO₃, Si₃N₄, CeO₂, MgO, SiO₂, andAl₂O₃) are milled down to micron size powders and then dispersed inwater up to about 16% by weight solid loading. The slurries may bedispensed into alumina crucibles via a commercial liquid handler undervigorous mixing. The homogenous solid mixture results after waterevaporation and firing the slurries at about 1200° C. to about 1700° C.under a reducing atmosphere (e.g., approximately 1% H₂ in air).

In another example process, the starting materials are combined via adry or wet blending process and fired in air or under a reducingatmosphere at about 1000° C. to about 1600° C. A fluxing agent (e.g.,sintering aids) may be added to the mixture before or during the step ofmixing. In some embodiments, the sintering aids may include, but are notlimited to, tetraethyl orthosilicate (TEOS), colloidal silica, lithiumoxide, titanium oxide, zirconium oxide, magnesium oxide, barium oxide,calcium oxide, strontium oxide, boron oxide, or calcium fluoride.Additional sintering aids include, but are not limited to, metal halides(e.g., NaCl, KCl, AlF₃, or NH₄Cl) and organic compounds such as urea. Insome embodiments, the phosphor composition comprises between about 0.01%and about 5%, between about 0.05% and about 5%, between about 0.1% andabout 4%, or between about 0.3% and about 1% by weight of the fluxmaterial(s) or sintering aid(s). The sintering aid can be intermixedwith the raw materials. For example, in some embodiments, tetraethylorthosilicate (TEOS) can be added to the raw materials to provide thedesired amount of sintering aid. In some embodiments, about 0.05% toabout 5% by weight of TEOS is provided to phosphor composition. In someembodiments, the amount of TEOS may be between about 0.3% and about 1%by weight.

The starting materials may be mixed together by any mechanical methodincluding, but not limited to, stirring or blending in a high-speedblender or a ribbon blender. The starting materials may be combined andsubjected to comminution in a bowl mill, a hammer mill, or a jet mill.The mixing may be carried out by wet milling, preferably when themixture of the starting materials is to be made into a solution forsubsequent precipitation. If the mixture is wet, it may be dried firstbefore being fired under a reducing atmosphere at a temperature fromabout 900° C. to about 1700° C. (preferably from about 1000° C. to about1600° C.) for a time sufficient to convert substantially all of themixture to the final composition.

The firing may be conducted in a batch-wise or continuous process,preferably with a stirring or mixing action to promote good gas-solidcontact. The firing time depends on the quantity of the mixture to befired, the rate of gas conducted through the firing equipment, and thequality of the gas-solid contact in the firing equipment. Typically, afiring time up to about 10 hours is adequate. The reducing atmospheretypically comprises a reducing gas such as hydrogen, carbon monoxide, ora combination thereof, optionally diluted with an inert gas, such asnitrogen or helium, or a combination thereof. Alternatively, thecrucible containing the mixture may be packed in a second closedcrucible containing high-purity carbon particles and fired in air sothat the carbon particles react with the oxygen present in air, thereby,generating carbon monoxide for providing a reducing atmosphere.

In some embodiments, the starting materials may be blended and dissolvedin a nitric acid solution. The strength of the acid solution is chosento rapidly dissolve the oxygen-containing compounds and the choice iswithin the skill of a person skilled in the art. Ammonium hydroxide isthen added in increments to the acidic solution. An organic base such asmethanolamine, ethanolamine, propanolamine, dimethanolamine,diethanolamine, dipropanolamine, trimethanolamine, triethanolamine, ortripropanolamine may be used in place of ammonium hydroxide.

The precipitate from the acidic solution may then be filtered, washedwith deionized water, and dried. The dried precipitate can be subject tocomminution (e.g., ball milled or otherwise thoroughly blended) and thencalcined in air at about 400° C. to about 1600° C. for a sufficient timeto ensure a substantially complete dehydration of the startingmaterials. The calcination may be carried out at a constant temperature.Alternatively, the calcination temperature may be ramped from ambienttemperatures and held at the final temperature for the duration of thecalcination. The calcined material is similarly fired at about 1000° C.to about 1600° C. for a sufficient time under a reducing atmosphere suchas H₂, CO, or a mixture of one of these gases with an inert gas.Alternatively, the reducing atmosphere may be generated by a reactionbetween a coconut charcoal and the products of the decomposition of thestarting materials to covert all of the calcined material to the desiredphosphor composition.

While the phosphor compositions can be suitable in many applicationsalone, the above phosphor composition may be intermixed with one or moreadditional phosphors for use in LED light sources.

Laminating and Sintering to Form a Ceramic Plate

The phosphor composition may be formed by laminating and sintering twoor more cast tapes to form a ceramic plate, where the cast tapes caninclude any of the compounds represented by Formulae I-VIII, orprecursors thereof. Examples and methods of laminating and sintering twoor more cast tapes are disclosed in U.S. Pat. No. 7,514,721 and U.S.Publication No. 2009/0108507, both of which are hereby incorporated byreference in their entirety.

First, the particle size of the raw materials (e.g., nitrate or oxidebased raw materials, such as Y₂O₃ and Al₂O₃ for forming YAG) mayoptionally be adjusted to reduce cracking in the cast tapes fromcapillary forces during evaporation of solvents. For example, theparticle size can be adjusted by pre-annealing raw material particles toobtain the desired particle size. Raw material particles can bepre-annealed in the temperature range of about 800° C. to about 1800° C.(or more preferably 1000° C. to about 1500° C.) to obtain the desiredparticle size. The pre-annealing may occur in a vacuum, air, O₂, H₂,H₂/N₂, or a noble gas (e.g., He, Ar, Kr, Xe, Rn, or combinationsthereof). In an embodiment, each of the raw materials is adjusted to beabout the same particle size. In another embodiment, the particles havea BET surface area in the range of about 0.5 m²/g to about 20 m²/g(preferably about 1.0 m²/g to about 10 m²/g, or more preferably about3.0 m²/g to about 6.0 m²/g).

A slurry may then be prepared for subsequently casting into a tape.Pre-made phosphors (e.g., phosphors prepared by flow-basedthermochemical synthetic routes described herein) and/or stoichiometricamounts of raw materials can be intermixed with various components toform a mixture. Examples of components for the mixture include, but arenot limited to, dopants, dispersants, plasticizers, binders, sinteringaids and solvents. The dopants, sintering aids, plasticizers, bindersand solvents may be the same as those described above with respect tothe molding and sintering process.

In some embodiments, the dispersants can be Flowen, fish oil, long chainpolymers, stearic acid, oxidized Menhaden fish oil, dicarboxylic acidssuch succinic acid, orbitan monooleate, ethanedioic acid, propanedioicacid, pentanedioic acid, hexanedioic acid, heptanedioic acid,octanedioic acid, nonanedioic acid, decanedioic acid, o-phthalic acid,p-phthalic acid and mixtures thereof.

The mixture may then be subjected to comminution to form a slurry by,for example, ball milling the mixture for a time period in the range ofabout 0.5 hrs. to about 100 hrs. (preferably about 6 hrs. to about 48hrs., or more preferably about 12 hrs. to about 24 hrs.). The ballmilling may utilize milling balls that include materials other than thecomponents intermixed within the mixture (e.g., the milling balls may beZrO₂). In an embodiment, the ball milling includes isolating the millingballs after a period of time by filtration or other known methods ofisolation. In some embodiments, the slurry has a viscosity in the rangeof about 10 cP to about 5000 cP (preferably about 100 cP to about 3000cP, or more preferably about 400 cP to 1000 cP).

Third, the slurry may be cast on a releasing substrate (e.g., a siliconecoated polyethylene terephthalate substrate) to form a tape. Forexample, the slurry may be cast onto a moving carrier using a doctorblade and dried to form a tape. The thickness of the cast tape can beadjusted by changing the gap between the doctor blade and the movingcarrier. In some embodiments, the gap between the doctor blade and themoving carrier is in the range of about 0.125 mm to about 1.25 mm(preferably about 0.25 mm to about 1.00 mm, or more preferably about0.375 mm to about 0.75 mm). Meanwhile, the speed of the moving carriercan have a rate in the range of about 10 cm/min. to about 150 cm/min.(preferably about 30 cm/min. to about 100 cm/min., or more preferablyabout 40 cm/min. to about 60 cm/min.). By adjusting the moving carrierspeed and the gap between the doctor blade and moving carrier, the tapecan have a thickness between about 20 μm and about 300 μm. The tapes mayoptionally be cut into desired shapes after casting.

Two or more tapes are laminated to form an assembly. The lamination stepcan include stacking two or more tapes (e.g., 2 to 100 tapes arestacked) and subjecting the stacked tapes to heat and uniaxial pressure(e.g., pressure perpendicular to the tape surface). For example, thestacked tapes may be heated above the glass transition temperature(T_(g)) of the binder contained in the tape and compressed uniaxiallyusing metal dies. In some embodiments, the uniaxial pressure is in therange of about 1 to about 500 MPa (preferably about 30 MPa to about 60MPa). In some embodiments, the heat and pressure is applied for a timeperiod in the range of about 1 min. to about 60 min. (preferably about15 min. to about 45 min., or more preferably about 30 min.). Thelamination step may optionally include forming various shapes (e.g.,holes or pillars) or patterns into the assembly by, for example, usingshaped dies.

Some embodiments of the assembly include at least one tape having aphosphor composition represented by any one of Formulae I-VIII. In someembodiments, all of the stacked tapes include a phosphor compositionrepresented by any one of Formulae I-VIII.

The assembly may be heated to form the composite. The heating step mayinclude a debinding process and a sintering process. The debindingprocess includes decomposing at least a portion of organic componentswithin the assembly (e.g., volatilize binders and plasticizers withinthe assembly). As an example, the assembly may be heated in air to atemperature in the range of about 300° C. to about 1200° C. (preferablyabout 500° C. to about 1000° C., or more preferably about 800° C.) at arate of about 0.1° C./min. to about 10° C./min. (preferably about 0.3°C./min. to about 5° C./min., or more preferably about 0.5° C./min. toabout 1.5° C./min). The example of a heating step may also includemaintaining the temperature for a time period in the range of about 30min. to about 300 min., which may be selected based upon the thicknessof the assembly.

The heating step also includes a sintering process to form thecomposite. The assembly may be sintered in a vacuum, air, O₂, H₂, H₂/N₂,or a noble gas (e.g., He, Ar, Kr, Xe, Rn, or combinations thereof) at atemperature in the range of about 1200° C. to about 1900° C. (preferablyabout 1300° C. to about 1800° C., or more preferably about 1350° C. toabout 1700° C.) for a time period in the range of about 1 hr. to about100 hrs (preferably about 2 hrs. to about 10 hrs.). In some embodiments,the debinding and sintering processes are completed in a single step.

The assembly may be sandwiched between cover plates during the heatingstep to reduce distortion (e.g., warping, cambering, bending, etc.) ofthe assembly. The cover plates may include materials having a meltingpoint above the temperatures applied during the heating step. Moreover,the cover plate may be sufficiently porous to permit transport ofvolatilized components through the covering plates. As an example, thecovering plate may be zirconium dioxide having a porosity of about 40%.

Molding and Sintering to Form a Ceramic Plate

The phosphor composition may be prepared by molding and sintering one ormore phosphors to form a ceramic plate. In some embodiments, thephosphor composition comprises a composition represented by any one ofFormulae I-VIII. Examples of ceramic plates and methods of making thesame are disclosed U.S. Publication No. 2009/0212697 and U.S.Application No. 61/315,763, both of which are hereby incorporated byreference in their entirety.

First, raw phosphor powders are provided, such as the phosphor powdersdescribed herein. The raw powders may be prepared using any conventionalor suitable methods, such as the flow-based thermochemical syntheticroutes described herein. In some embodiments, raw powders of phosphormaterials used to make the composite are typically nano-sized particleswith average particle size no greater than about 1000 nm, preferably nogreater than about 500 nm, more preferably no greater than 200 nm. Ifthe particle size is greater than about 1000 nm, it can be verydifficult to make total light transmittance higher than about 50%,because such large particles do not easily fuse with each other even ata high temperature and high pressure sintering condition. The resultwould be a tendency for a lot of air voids to remain in the ceramicplate. On the other hand, nano-sized particles can easily fuse with eachother, which enable us to prepare fine and air void free ceramic plates.The raw materials are not required to have the same composition orcrystal structure of resultant phosphor ceramic plate.

In some embodiments, small quantities of flux materials (e.g., sinteringaids) may be used in order to improve sintering properties if desired.In some embodiments, the sintering aids may include, but are not limitedto, tetraethyl orthosilicate (TEOS), colloidal silica, lithium oxide,titanium oxide, zirconium oxide, magnesium oxide, barium oxide, calciumoxide, strontium oxide, boron oxide, or calcium fluoride. Additionalsintering aids include, but are not limited to, alkali metal halidessuch as NaCl or KCl, and organic compounds such as urea.

Various plasticizers may also be included, in some embodiments, toreduce the glass transition temperature and/or improve flexibility ofthe ceramic. Non-limiting examples of plasticizers includedicarboxylic/tricarboxylic ester-based plasticizers, such asbis(2-ethylhexyl) phthalate, diisononyl phthalate,bis(n-butyl)phthalate, butyl benzyl phthalate, diisodecyl phthalate,di-n-octyl phthalate, diisooctyl phthalate, diethyl phthalate,diisobutyl phthalate, and di-n-hexyl phthalate; adipate-basedplasticizers, such as bis(2-ethylhexyl)adipate, dimethyl adipate,monomethyl adipate, and dioctyl adipate; sebacate-based plasticizers,such as dibutyl sebacate, and maleate; dibutyl maleate; diisobutylmaleate; polyalkylene glycols such as polyethylene glycol, polypropyleneglycol, and copolymers thereof; benzoates; epoxidized vegetable oils;sulfonamides, such as N-ethyl toluene sulfonamide,N-(2-hydroxypropyl)benzene sulfonamide, and N-(n-butyl)benzenesulfonamide; organophosphates, such as tricresyl phosphate, tributylphosphate; glycols/polyethers, such as triethylene glycol dihexanoate,tetraethylene glycol diheptanoate; alkyl citrates, such as triethylcitrate, acetyl triethyl citrate, tributyl citrate, acetyl tributylcitrate, trioctyl citrate, acetyl trioctyl citrate, trihexyl citrate,acetyl trihexyl citrate, butyryl trihexyl citrate, and trimethylcitrate; alkyl sulphonic acid phenyl ester; and mixtures thereof.

Next, the raw materials may be mixed together and formed into a mold. Insome embodiments, the mixing and molding process may be made easier byoccasionally adding binder resin and solvent to the raw powders. Abinder is any substance that improves adhesion of the particles of thecomposition being heated to form a composite. Some non-limiting examplesof binders include polyvinyl alcohol, polyvinyl acetate, polyvinylchloride, polyvinyl butyral, polystyrene, polyethylene glycol,polyvinylpyrrolidones, polyvinyl acetates, and polyvinyl butyrates, etc.In some, but not all, circumstances, it may be useful for the binder tobe sufficiently volatile that it can be completely removed or eliminatedfrom the precursor mixture during the sintering phase. Solvents whichmay be used in include, but not limited to water, a lower alkanol suchas but not limited to denatured ethanol, methanol, isopropyl alcohol andmixtures thereof, preferably denatured ethanol, xylenes, cyclohexanone,acetone, toluene and methyl ethyl ketone, and mixtures thereof. In apreferred embodiment, the solvent is a mixture of xylenes and ethanol.

The mixing process can be done using a mortar and pestle, ball millingmachine, bead milling machine or other equivalent equipments. For themolding process, a simple die for tablet molding, hot isostatic pressing(HIP), or cold isostatic pressing (CIP) may be utilized. In someembodiments, controlled quantities of raw powders are loaded in a moldfollowed by applying pressure to form the plate. The mold is thensintered at a high temperature that does not exceed the melting point ofthe resultant phosphor materials.

Any kinds of suitable ceramic sintering techniques can be used toprepare translucent ceramic plates. In some embodiments, sintering maybe carried out while applying pressure. Sintering conditions such as thetemperature profile, atmosphere, pressure, and duration will depend onthe type of phosphor material.

Lighting Apparatuses

The phosphor compositions disclosed herein may be included within alighting apparatus. Various configurations for the lighting apparatusare within the scope of the present application. FIGS. 1-2 (not drawn toscale) provide non-limiting examples of lighting apparatuses within thescope of the present application. FIG. 1 is an exemplary lightingapparatus having a phosphor powder composition. A submount 10 has alight source 15, such as a conventional base LED mounted thereon. Thelight source 15 is adjacent to encapsulated phosphor powder 20 whichreceives at least a portion of the light emitted from the light source15. An optional encapsulant resin 25 is placed over the light source 15and the encapsulated phosphor powder 20. The encapsulated phosphorpowder 20 can include any of the co-doped phosphor compositionsdisclosed in the present application. For example, the encapsulatedphosphor powder 20 can include the phosphor composition of Formula I.

The phosphor compositions may be encapsulated in a mold (e.g., asillustrated in FIG. 1 by encapsulant resin 25). For example, thecomposition may be formed into a mold by encapsulating the phosphorcomposition in a resin, such as an epoxy or silicone. Examples andmethods for encapsulating the phosphors are disclosed in U.S. Pat. Nos.5,998,925 and 6,069,440, both of which are hereby incorporated byreference in their entirety. Briefly, a powder form of the phosphorcomposition may be intermixed with a resin to form a slurry. The slurrymay then be cured to form the mold.

In some embodiments, the phosphor composition is intermixed with anoptional second phosphor and disposed within the lighting apparatus. Forexample, a mixture of the phosphor composition of Formula I and a secondphosphor (e.g., YAG:Ce) may be prepared and subsequently encapsulatedwithin a resin.

FIG. 2A is another example of a lighting apparatus where the phosphorcomposition is contained within an emissive layer 30 (e.g., the emissivelayer is a sintered ceramic plate as discussed above) which receives atleast a portion of the light emitted from the light source 15. Emissivelayer 30 can, for example, be a ceramic plate including the phosphorcomposition. In some embodiments, the emissive layer 30 includes thephosphor composition and an optional second phosphor. For example, theemissive layer 30 may include the phosphor composition of Formula I anda second phosphor (e.g., YAG:Ce).

FIG. 2B is still another example of a lighting apparatus where thephosphor composition and an optional second phosphor are containedwithin separates emissive layers. The first emissive layer 40 isdisposed above light source 15 and receives at least a portion of thelight emitted from the light source 15. First emissive layer 40 can, forexample, be a ceramic plate including the phosphor composition and/orthe optional second phosphor. The second emissive layer 35 is disposedbetween the first emissive layer 40 and the light source 15. The secondemissive layer 35 also receives at least a portion of the light emittedfrom the light source 15. Second emissive layer 35 can, for example, bea ceramic plate including the phosphor composition and/or the optionalsecond phosphor. In some embodiments, the first emissive layer 40comprises the phosphor composition and the second emissive layer 35comprises the optional second phosphor. In some embodiments, the firstemissive layer 40 comprises the optional second phosphor and the secondemissive layer 35 comprises the phosphor composition.

The location of the various components in FIGS. 1-2 (e.g., the lightsource, the phosphor composition, etc.) are for illustrative purposesand not intended to be limiting. In some embodiments, the components areconfigured so that the phosphor composition receives at a least aportion of the radiation emitted from the light source. In someembodiments, the components are configured so that the optional secondphosphor receives at a least a portion of the radiation emitted from thelight source.

The light source (e.g., as illustrated in FIGS. 1-2 by light source 15)may, in some embodiments, be configured to emit blue radiation. Forexample, the blue radiation may include a wavelength of peak emissionbetween about 430 nm and about 550 nm. In some embodiment, the lightsource emits blue radiation having a wavelength of peak emission ofabout 450 nm. Some embodiments include a light source that is asemiconductor LED. As an example, the light source may be an AlInGaNbased single crystal semiconductor material coupled to an electricsource.

The lighting apparatuses of the present application may advantageouslyproduce a broad emission spectrum. The lighting apparatuses may, in someembodiments, emit radiation including a peak wavelength between about500 nm and about 650 nm. The phosphor lighting apparatus may, in someembodiments, emit radiation including a first wavelength of peakemission between about 515 nm and about 560 nm and a second wavelengthof peak emission between about 600 and about 615 nm. In someembodiments, the lighting apparatuses emit radiation including a thirdwavelength of peak emission between about 730 nm and about 770 nm.

The lighting apparatuses may also exhibit a high CRI and/or low CCT. Forexample, the lighting apparatus can emit light with a CRI of at leastabout 70. In some embodiments, the CRI is at least about 80; at leastabout 90; or about 91. The reference CCT may be in the range of about2500 K to about 10000 K; in the range of about 2500 K to about 5000 K;in the range of about 2500 K to about 4500 K; or in the range of about2600 to about 3400 K.

Methods of Using the Phosphor Composition

Also disclosed herein are methods of producing light including exposingthe phosphor composition to blue radiation. For example, the phosphorcomposition may be represented by any one of Formulae I-VIII. In someembodiments, the blue radiation has a wavelength of peak emissionbetween about 430 nm to about 550 nm. In some embodiments, the blueradiation has a wavelength of peak emission of about 450 nm.

The methods of the present application may advantageously produce abroad emission spectrum. The method may, in some embodiments, produceradiation including a peak wavelength between about 500 nm and about 650nm. The method may, in some embodiments, produce radiation including afirst wavelength of peak emission between about 515 nm and about 560 nmand a second wavelength of peak emission between about 600 and about 615nm. In some embodiments, the methods produce radiation having a thirdwavelength of peak emission between about 730 nm and about 770 nm.

The method may also produce light with a high CRI and/or low CCT. Forexample, the method can produce light with a CRI of at least about 70.In some embodiments, the CRI is at least about 80; at least about 90; orabout 91. The reference CCT may be in the range of about 2500 K to about10000 K; in the range of about 2500 K to about 5000 K; in the range ofabout 2500 K to about 4500 K; or in the range of about 2600 to about3400 K.

EXAMPLES

Additional embodiments are disclosed in further detail in the followingexamples, which are not in any way intended to limit the scope of theclaims.

Example 1 Preparing Phosphor Compositions

Lu_(2.0)Ce_(0.16)Ca_(0.84)Al_(3.84)Mn_(0.16)SiO₁₂ was prepared by handmixing the following ingredients into a methanol slurry until the slurrydried: 5 g of Lu₂O₃, 0.345 g of CeO₂, 1.055 g of CaCO₃, 2.46 g of Al₂O₃,0.23 g of MnCO₃ and 0.755 g of SiO₂. This mixture was then transferredinto an alumina boat and heated to 600° C. in air at a ramp rate of 4°C./min. Subsequently, H₂/N₂ gas was passed over the heated mixture andthe temperature increased to 1500° C. at a heating rate of 4° C./min.The temperate was maintained at 1500° C. for 5 hours and then cooled toroom temperature while still exposed H₂/N₂. The lump was crushed by handinto powder to yield Lu_(2.0)Ce_(0.16)Ca_(0.84)Al_(3.84)Mn_(0.16)SiO₁₂(Composition 1) for further investigation.

Various examples of compositions represented by Formula I are disclosedin TABLE 1, where compositions having more than one element in a columndenote a combination of each element at a 1 to 1 molar ratio. Forexample, Composition 16 has about equal molar parts of Ca and Sr as themain group element (MG). Compositions 2-27 were prepared using similarmethods as described above. Compositions 28-30 may also be preparedusing similar methods as described above.

TABLE 1 Composition RE Ak MG x y z e r 1 Lu Ca Al 0.16 0.16 0.16 0 0 2Lu Ca Al 0.20 0.16 0.16 0 0 3 Lu Ca Al 0.12 0.16 0.16 0 0 4 Lu Ca Al0.08 0.16 0.16 0 0 5 Lu Ca Al 0.06 0.16 0.16 0 0 6 Lu Ca Al 0.04 0.160.16 0 0 7 Lu Ca Al 0.02 0.16 0.16 0 0 8 Lu Ca Al 0.01 0.16 0.16 0 0 9Lu Ca Al 0.005 0.16 0.16 0 0 10 Lu Ca Al 0.16 0.40 0.40 0 0 11 Lu Ca Al0.16 0.28 0.28 0 0 12 Lu Ca Al 0.16 0.12 0.12 0 0 14 Lu Ca Al 0.16 0.080.08 0 0 15 Lu Ca Al 0.16 0.04 0.04 0 0 16 Lu Ca, Sr Al 0.16 0.16 0.16 00 17 Lu Ca, Ba Al 0.16 0.16 0.16 0 0 18 Lu, Y Ca Al 0.16 0.16 0.16 0 019 Lu, Tb Ca Al 0.16 0.16 0.16 0 0 20 Lu, Gd Ca Al 0.16 0.16 0.16 0 0 21Lu Ca Al, In 0.16 0.16 0.16 0 0 22 Lu Ca Al, 0.16 0.16 0.16 0 0 Ga 23 LuCa Al 0.16 0 0.02 0 0 24 Lu Ca Al 0.16 0 0.16 0.16 0 25 Lu Ca Al 0.160.16 0.16 0 0.5 26 Lu Ca Al 0.16 0.16 0.16 0 1.0 27 Lu Ca, Mg Al 0.160.16 0.16 0 1.0 28 Lu Ca Al 0.16 0 0.02 0.02 0 29 Lu Ca Al 0.16 0 0.040.04 0 30 Lu Ca Al 0.16 0 0.08 0.08 0

Example 2 Evaluating Luminescence of Phosphor Powders

The luminescence efficiency of phosphor powder was evaluated bymeasuring the emission from the phosphor powders irradiated by standardexcitation light with a predetermined intensity. The internal quantumefficiency (IQE) of a phosphor is the ratio of the number of photonsgenerated from the phosphor to the number of photons of excitation lightwhich penetrate into the phosphor.

The IQE of a phosphor material can be expressed by the followingformula:

${InternalQuantumEfficiency} = \frac{\int{{\lambda \cdot {P(\lambda)}}{\lambda}}}{\int{{\lambda \cdot {E(\lambda)} \cdot \left\lbrack {1 - {R(\lambda)}} \right\rbrack}{\lambda}}}$ExternalQuantumEfficiency(λ) = InternalQuantumEfficiency(λ) ⋅ [1 − R(λ)]Absorption(λ) = 1 − R(λ)

where at any wavelength of interest λ, E(λ) is the number of photons inthe excitation spectrum that are incident on the phosphor, R(λ) is thenumber of photons in the spectrum of the reflected excitation light, andP(λ) is the number of photons in the emission spectrum of the phosphor.This method of IQE measurement is also provided in Ohkubo et al.,“Absolute Fluorescent Quantum Efficiency of NBS Phosphor StandardSamples,” 87-93, J. Illum. Eng. Inst. Jpn. Vol. 83, No. 2, 1999, thedisclosure of which is incorporated herein by reference in its entirety.

Example 2.1 Luminescence Properties ofLu_(2.0)Ce_(0.16)Ca_(0.84)Al_(3.84)Mn_(0.16)SiO₁₂

FIG. 3 shows the excitation spectrum of Composition 1(Lu_(2.0)Ce_(0.16)Ca_(0.84)Al_(3.84)Mn_(0.16)SiO₁₂). The excitationspectrum includes a relatively wide range from about 390 nm to about 510nm. Composition 1 may therefore be excited by blue light (e.g., about450 nm) typically used in conventional white-LEDs. FIG. 4 shows theemission spectrum for Composition 1 when excited by radiation of about450 nm. The composition exhibits two wavelengths of peak emission atabout 510 nm and about 600 nm.

Example 2.2 Effect of Doping Concentration on Emission Spectra

FIG. 5 shows the emission spectra of Compositions 1-9, where thevariable x is varied from 0.05 to 0.20. The Ce percentages shown in FIG.5 correlate with half the value of x. For example, 10% Ce is Composition2 and therefore correlates with x being 0.20. The peak emission at about600 nm increases with increasing Ce concentration. The peak also veryslightly exhibits red-shifting with increasing Ce concentration. FIG. 6shows the emission spectra of Compositions 1 and 10-15. The Mnpercentages shown in FIG. 6 correlate with a quarter of the value of z.For example, 10% Mn is Composition 10 and therefore correlates with zbeing 0.40. When Mn is more than about 4%, an additional peak around 750nm appears.

Example 2.3 Quantum Efficiencies of Phosphor Compositions

FIG. 7 shows the quantum efficiencies when varying the amount Ce.Compositions 2-7 were measured, where the percentages shown in FIG. 7correlate with half the value of x. The IQE percentage remainsrelatively constant with increasing Ce concentrations, whereas the EQEand Abs. percentages exhibit an initial increase followed by a plateauat about 6% Ce (i.e., x is about 0.12). FIG. 8 compares the quantumefficiencies for various Mn concentrations. Compositions 1, 10, 11, 14and 15 were measured, where the percentages shown in FIG. 8 correlatewith a quarter of the value of z. The quantum efficiencies generallydecrease with increasing amounts of Mn.

Example 2.4 Effect of Host on Luminescence

FIG. 9 compares the emission spectra of various compositions withmodified hosts. Compositions 16-22 are shown in FIG. 7. The IQE forCompositions 16-22 was 52.66%, 60.85%, 60.68%, 30.16%, 35.86%, 36.82%,and 49.74%, respectively. The peak emission at about 600 nm is enhancedwhen 50% Gd or Tb is included as a host; however the IQE was lower forthese compositions. The IQE was about 60% for compositions including 50%Sr, Ba, and Y.

Example 2.5 Comparison of Phosphor Composition with Existing Phosphors

FIG. 10 compares the emission spectrum of commercial YAG:Ce phosphors(Yttrium Aluminum Garnet, Product No.: BYWO1A/P TCWO1AN, PhosphorTechCorp., Lithia Springs, Ga., USA) with Composition 1. The co-dopedphosphor exhibits a wider emission spectrum compared to conventionalYAG:Ce. As shown in TABLE 2, this spectrum provides an improved CRI ofabout 91, whereas YAG:Ce exhibits a CRI of 71. The x and y coordinatesand color temperature are also provided in TABLE 2.

TABLE 2 Phosphor x y CT, K Ra Ce³⁺ and Mn²⁺ co-doped 0.3480 0.3528 489291 Lu₂CaAl₄SiO₁₂ Ce³⁺ doped YAG 0.3218 0.3426 5976 71.9

Example 3 Preparation of Raw Particles Using Inductively Coupled RFThermal Plasma Pyrolysis

Phosphor powders of Lu_(2.0)Ce_(0.16)Ca_(0.84)Al_(3.84)Mn_(0.16)SiO₁₂were prepared using inductively coupled RF thermal plasma pyrolysis.106.287 g Lu(NO₃)_(3.6)H₂O, 25.03 g Ca(NO₃)₂.4H₂O, 182.625 gAl(NO₃)₃.9H₂O, 5.79 g Mn(NO₃)₂.6H₂O, 8.686 g Ce(NO₃)₃.6H2O and 68.605 gof 22-25% Aminopropylsilane triol were dissolved along with 650 g Ureain about 720 mL of water, followed by ultrasonication for 30 min toprepare the transparent precursor solution. This precursor solution of0.4 M was carried into a plasma reaction chamber via an atomizationprobe using a liquid pump.

All deposition experiments were conducted with an RF induction plasmatorch (TEKNA Plasma System, Inc PL-35) operating at 3.3 MHz. For thedeposition experiments, the chamber pressure was kept at around 25kPa-35 kPa, and the RF generator plate power was in the range of 10-12kW. Both the plate power and the deposition pressure are user-controlledparameters. Argon was introduced into the plasma torch as both theswirling sheath gas and the central plasma gas via the gas inlet ports.Sheath gas flow was maintained at 30 slm (standard liters per minute),while central gas flow was 10 slm.

Reactant injection was performed using a radial atomization probe (TEKNAPlasma System, Inc SDR-772). The probe was positioned at the center ofthe plasma plume during reactant injection. The reactants were fed intothe plasma plume at a rate of 10 ml/min during deposition. Atomizationof the liquid reactant was performed with Argon as atomizing gasdelivered at a flow rate of 15 slm. The cooling water supply to theatomization probe was maintained at a flow rate of 4 slm and at apressure of 1.2 MPa, as recommended by the manufacturer.

Example 4 Preparation of Sintered Ceramic Plates of Lu₂CaAl₄SiO₁₂:Ce, Mn

Sintered ceramic plates were made using Lu₂CaAl₄SiO₁₂:Ce, Mn phosphornano-powders. 4 g of nano-powder prepared by the method described inExample 3, 0.21 g of poly(vinyl butyral-co-vinyl alcohol-co-vinylacetate) (average Mw 90,000-120,000 powder, Sigma-Aldrich), 0.012 g offumed silica powder (CAB-O-SIL® HS-5, Cabot Corporation), and 10 ml ofmethanol were well mixed by mortar and pestle until the mixture slurrysolution became very smooth. By blowing hot air form a dryer and keepthe pestle moving, methanol was completely removed, and then dry powderswere obtained. By varying the loading quantities as 45.0, 47.5, 50.0,and 52.5 mg, the obtained dry powders were spread out into die set with3 mm of diameter (Product#: 0012-6646, 3 mm KBr Die Set, InternationalCrystal Laboratories, Inc) followed by applying a pressure of 4000 psiusing hydraulic press. Then the obtained plates were sintered at 1500°C. for 5 hrs (heating rate is 5° C./min) using a tube furnace, Model No.GSL 1800X (MTI Corporation, Richmond, Calif., USA) under a reducingatmosphere (e.g., 3% or 4% Hydrogen-97% or 96% nitrogen atmosphere) orvacuum condition. The crystalline phase of all ceramic plate samples wasdetermined as Lu₂CaAl₄SiO₁₂ garnet by XRD.

Example 5 Optical measurement of Ceramic Plates

The four ceramic plates from Example 5 were mounted onto a blue LED tipand 10 mA DC at 2.9V was applied to the LED. The white light spectrumwas acquired for each sample using a photo detector together with anintegrating sphere (MCPD 7000, Otsuka Electronics, Inc). In order toremove any air gaps between ceramic plate and LED tip, paraffin oil wasfilled into the gap. The identical LED tip and operation conditions wereemployed for each measurement.

From these emission spectra, CIE color chromaticity (x, y) wascalculated. TABLE 3 includes the results for the ceramic plate alongwith the same co-doped phosphor powder in Example 2.5. The emissionspectra for the ceramic plate is shown in FIG. 11. For comparison, FIG.12 shows the emission spectra for the phosphor powder composition fromExample 3.

TABLE 3 Ceramic Plate Powder Chromaticity (x, y) (0.329, 0.339) (0.320,0.337) CCT 5640K 6070K CRI 87 87 R9 40 21

In addition, total light transmittance data of one of the samples wasalso measured using a similar measurement system as described in U.S.Patent Publication No. 2009/0212697 (MCPD 7000, Otsuka Electronics, Inc,Xe lamp, monochromator, and integrating sphere equipped).Photoluminescent spectrum of the sample was excited by a blue light (thepeak wavelength was about 460 nm) from a monochromator that was acquiredusing the same photo detector. The peak wavelength of theLu₂CaAl₄SiO₁₂:Ce, Mn ceramic plate was around 530 nm, and the totallight transmittance at 530 nm was about 42%.

1. A phosphor composition comprising a compound represented by theformula (RE_(2−x+y)Ce_(x)Ak_(1−y))(MG_(4−z−r),Si_(r)Mn_(z))(Si_(1−e)P_(12−r)N_(r), wherein: RE comprises at least onerare earth metal; Ak comprises at least one alkaline earth metal; MGcomprises at least one main group element; x is greater than 0 and lessthan or equal to 0.2; y is less than 1; z is greater than 0 and lessthan or equal to 0.8; e is about 0, or less than or equal to 0.16; r isabout 0, or less than or equal to 1; and z is about the sum of e and y.2. The phosphor composition of claim 1, wherein MG is selected from thegroup consisting of Al, Sc, In, Ga, B, Si and combinations thereof. 3.The phosphor composition of claim 2, wherein MG is Al.
 4. The phosphorcomposition of claim 1, wherein RE is selected from the group consistingof Lu, Y, Gd, Tb, Sm, Pr and combinations thereof.
 5. The phosphorcomposition of claim 4, wherein RE is Lu.
 6. The phosphor composition ofclaim 1, wherein Ak is selected from the group consisting of Mg, Ca, Ba,Sr and combinations thereof.
 7. The phosphor composition of claim 6,wherein Ak is Ca.
 8. The phosphor composition of claim 1, the compoundis represented by the formula(Lu_(2.16−x)Ce_(x))Ca_(0.84)Al_(3.84)Mn_(0.16) SiO₁₂, wherein x isgreater than 0.0025 and less than 0.2.
 9. The phosphor composition ofclaim 8, wherein x is about 0.16.
 10. The phosphor composition of claim1, wherein the compound is represented by the formula(Lu_(1.84+z)Ce_(0.16))Ca_(1−z)(Al_(4−z)Mn_(z))SiO₁₂, wherein z isgreater than 0 and less than 0.8.
 11. The phosphor composition of claim10, wherein z is about 0.02 or about 0.04.
 12. The phosphor compositionof claim 1, wherein the compound is represented by the formula(Lu_(1.84)Ce_(0.16))Ca(Al_(4−z)Mn_(z))(Si_(1−z)P_(z))O₁₂, wherein z isat least about 0.01 and less than about 0.16.
 13. The phosphorcomposition of claim 12, wherein z is about 0.02 or about 0.04.
 14. Thephosphor composition of claim 1, wherein the composition is representedby the formula selected from the group consisting of(Lu_(1.86)Ce_(0.16)Ca_(0.98))(Al_(3.98)Mn_(0.02))SiO₁₂,(Lu_(1.88)Ce_(0.16)Ca_(0.96))(Al_(3.96)Mn_(0.04))SiO₁₂,(Lu_(1.84)Ce_(0.16))Ca(Al_(3.98)Mn_(0.02))(Si_(0.98)P_(0.02))SiO₁₂ and(Lu_(1.84)Ce_(0.16))Ca(Al_(3.96)Mn_(0.04))(Si_(0.96)P_(0.04))O₁₂. 15.The phosphor composition of claim 1, wherein the compound is representby the formula (Lu_(2−x+z) Ce_(x)Ca_(1−z)) (Al_(4−z−r)Si_(r)Mn_(z))SiO_(12−r)N_(r), wherein: x is greater than about 0.001 and less thanabout 0.4; z is greater than about 0.001 and less than about 0.4; and ris greater than about 0.2 and less than or equal to about
 1. 16. Thephosphor composition of claim 15, wherein the compound is represented bythe formula selected from the group consisting of(Lu_(2.0)Ce_(0.16)Ca_(0.84))(Al_(3.44)Si_(0.40)Mn_(0.16))SiO_(11.6)N_(0.40)and (Lu_(2.0)Ce_(0.16)Ca_(0.84))(Al_(2.84)Si_(1.0)Mn_(0.16))SiO₁₁N₁. 17.The phosphor composition of claim 1, wherein the phosphor composition isa sintered ceramic plate.
 18. The phosphor composition of claim 1,wherein the phosphor composition comprises a particulate that includesthe compound.
 19. A lighting apparatus comprising: a light sourceconfigured to emit blue radiation; and the phosphor composition of claim1, wherein the phosphor composition is configured to receive at a leasta portion of the blue radiation.
 20. A method of producing lightcomprising exposing the phosphor composition of claim 1 to a blueradiation.